yeast strains resistant to Potassium Sorbate?

I foolishly purchased some commercial cider not realizing it had potassium sorbate, which I now understand kills yeast. I used some yeast nutrient, and it seemed to get it going, but after three weeks it is still mostly sweet. Is there a way to save this batch by, say, introducing a hardier strain of yeast that is resistant to the preservative?

I don't know of any yeast strains (even wild yeast) that would ferment something with sorbate in it. I'm surprised it even started to ferment. Sorry I can't be more helpful!

Over the summer, when I ran out of cider from last year, I fermented 3 single gallons of Zieglers cider (which has k-sorbate) with Nottingham, S04 and US05. They all fermented out but didnt taste very good. The S04 and US05 started the fastest (10 hrs later). The nottingham didnt really get started until 48 hours later, but it tasted the best - at least for a while. It was decent but a little too sweet when I checked it at day seven at 1.012. When I checked it again at day 9 it was at 1.002 and watery tasting. The S04 and US05 batches tasted thin and bland from the get-go and never improved, but they did ferment out to 1.000 by day 7. I ended up dumping them all. You might want to give nottingham a shot and either dont let the sg drop too low or else hopefully you will have better luck on the residual flavor

From what understand is Pot Sorbate does not kill yeast, it stops the yeast from reproducing. So my guess is it fermented until all the viable yeast died out and where unable to reproduce. I would buy an apple juice with no preservatives and make a strong healthy starter to get things going.

How to Brew - By John Palmer - Preparing Yeast and Yeast Starters